CSTB Human

Cystatin B functions primarily as an intracellular cysteine protease inhibitor. It inhibits the activity of several proteases, including papain and cathepsins L, H, and B . The protein can form a dimer stabilized by noncovalent forces, which enhances its inhibitory function . This inhibition is crucial for protecting cellular components from the potentially harmful effects of proteases that may leak from lysosomes .

Recombinant human Cystatin B is typically produced in E. coli. The recombinant protein often includes an N-terminal 7-His tag to facilitate purification . The protein is usually purified to a high degree, with a purity of over 95% as determined by SDS-PAGE under reducing conditions . The recombinant form is used in various research applications, including studies on protease inhibition and protein-protein interactions.

Mutations in the CSTB gene are associated with Progressive Myoclonus Epilepsy (EPM1), a rare genetic disorder characterized by muscle jerks (myoclonus) and seizures . The exact mechanism by which these mutations lead to EPM1 is still under investigation, but it is believed that the loss of cystatin B’s inhibitory function may result in uncontrolled protease activity, leading to neuronal damage.

Recombinant Cystatin B is used in various biochemical assays to study its inhibitory effects on cysteine proteases. It is also employed in research focused on understanding the molecular mechanisms underlying EPM1 and other related disorders .

The recombinant protein is typically lyophilized and should be reconstituted in a suitable buffer before use. It is stable for several months when stored at -20°C to -70°C under sterile conditions . Repeated freeze-thaw cycles should be avoided to maintain its activity.